Tsunami Evacuation Zones

Tsunami Evacuation Zones: Version 1.0 December 2008 1

Tsunami Evacuation ZonesDirector’s Guideline for Civil Defence Emergency Management Groups [DGL 08/08]

Resilient New ZealandAotearoa Manahau

2 Tsunami Evacuation Zones: Version 1.0 December 2008

Tsunami Evauation ZonesDirector’s Guideline for Civil Defence Emergency Management Groups[DGL 08/08]

December 2008ISBN 978-0-478-25483-9

AuthorityThis document has been issued by the Director of the Ministry of Civil Defence & Emergency Management pursuant to s9(3) of the Civil Defence Emergency Management (CDEM) Act 2002. It provides guidance to CDEM Groups in the development of plans. CDEM Groups are required to take account of this guideline in their planning (s53(2)).

Ministry of Civil Defence & Emergency ManagementPO Box 5010WellingtonNew Zealand

Tel: +64 4 473 7363Fax: +64 4 473 7369email: [email protected]


Foreword ............................................................................................................................ 4

Background ....................................................................................................................... 5

Purpose of this information .............................................................................................. 6

Tsunami evacuation zones .............................................................................................. 7

The optimum number of evacuation zones ..................................................................... 7

Recommended number of evacuation zones ................................................................. 7

Establishing evacuation zone boundaries ....................................................................... 8

Defining evacuation zone boundaries ........................................................................... 9

Four developmental levels ................................................................................................ 9

Minimum standards and improving zone boundaries over time ................................. 11

Accommodating existing hazard or evacuation zone information ............................... 11

Other considerations in defining evacuation zones ...................................................... 11

Tsunami evacuation maps ............................................................................................ 13

Map scale ........................................................................................................................ 13

Legend text ...................................................................................................................... 13

Principles for warning and evacuation information on maps....................................... 14

Recommended text for warning and evacuation information ...................................... 14

Placement and availability ............................................................................................. 15

Information board example ............................................................................................ 16

Signage for tsunami information ................................................................................. 17

Community participation in evacuation planning ..................................................... 18

References....................................................................................................................... 19

Table of Contents


The Indian Ocean tsunami of December 26th, 2004 greatly raised awareness of the potential threat tsunami pose to New Zealand. Reports commissioned by the Ministry of Civil Defence & Emergency Management in 2005 calculated the risk to New Zealand from tsunami as similar to the risk from large earthquakes. Consequently, the science and civil defence emergency management (CDEM) sectors in New Zealand have directed greater effort to improving the understanding of New Zealand’s tsunami hazards and risks, and enhancing tsunami emergency response arrangements. The goal is increased individual and community resilience to tsunamis.

The Tsunami Working Group was established in 2007 to coordinate and support national efforts in the development of a comprehensive tsunami risk management programme. In 2007 the Tsunami Working Group investigated international and domestic practice on tsunami signage and, as a result, a technical standard for National Tsunami Signage (TS 01/08) was published in April 2008.

In early 2008 the working group coordinated a workshop involving CDEM and science agencies to examine a nationally consistent, best practice approach to the development of tsunami evacuation zones and maps. This document details the recommendations which were agreed in that workshop and developed through subsequent feedback from six regional seminars held in June and July 2008.

We are indebted to all those who participated in the development and review of this information.The objective of this document is to support an evidence-based approach to the development of tsunami evacuation zones and maps, which is consistent across New Zealand communities. In this way we can be sure that New Zealanders, no matter where they live or work, can become better prepared.

John HamiltonDirector Ministry of Civil Defence & Emergency Management

Foreword


Tsunamis are a threat to life and property for all people that live, work and play near the New Zealand coast. The devastating events in the Indian Ocean on December 26, 2004 alerted the New Zealand public to the potential catastrophe of large tsunami waves inundating populated coastal areas. At the request of the Minister of Civil Defence, the Ministry of Civil Defence & Emergency Management commissioned a national tsunami risk and preparedness review. The resulting reports, prepared by GNS Science, on Tsunami Hazard and Risk in New Zealand (compiled by Berryman, 2005) and New Zealand’s Preparedness for Tsunami Hazard (compiled by Webb, 2005), highlighted both the level of risk posed by tsunami and the opportunities for improving New Zealand’s tsunami resilience.

The findings of these reviews have established a basis for a prioritised national programme of work in tsunami risk management. In March 2007 the Tsunami Working Group was established with representatives from CDEM. The aims of this working group were to identify the components of a comprehensive end-to-end tsunami warning system and to select areas of work to address current gaps.

The national work programme has identified four key areas for advancement:

1. Knowledge of tsunami hazard risks,2. Warning system development,3. Planning for response,4. Awareness of tsunami risks and what to do.

Two areas of work identified as key to the planning and awareness work streams were the development of a nationally agreed standard for the appearance and placement of tsunami signage and, flowing from this, establishment of a nationally consistent approach for the development of tsunami evacuation zones and maps. Tsunami signage was the focus of a sub-committee of the Tsunami Working Group in 2007 and a National Tsunami Signage Technical Standard for the CDEM Sector (TS 01/08) was published in April 2008.

A multi-agency workshop was coordinated by the Tsunami Working Group in March 2008 to develop an agreed position on evacuation zones and map methodology and content. The findings of this workshop were circulated widely for comment within CDEM, including through six regional seminars held in June and July 2008. The outputs of that process (Leonard, 2008) have provided the basis for the material included in this Director’s Guildeline.

Background


Evacuation planning is a fundamental component of emergency planning for tsunami. This document provides information for Local Authorities and CDEM Groups to support the development of local tsunami evacuation zones, maps, and information that is nationally consistent. This document does not provide detailed guidance on evacuation planning processes for tsunami. Guidance for mass evacuation planning is provided in the Director’s Guideline DGL 07/08 Mass Evacuation Planning.

The benefits of a consistent approach to mapping tsunami evacuation zones are expected to include: • Support for a common understanding across New Zealand communities of

tsunami evacuation zones, maps, evacuation signage and tsunami response actions.

• Improved alignment of tsunami evacuation planning with processes for official tsunami warnings.

The intention of this document is not to be prescriptive regarding the level of risk used as a basis for establishing hazard zones and/or evacuation zones. Rather it makes recommendations regarding an approach agreed by CDEM for the development and display of evacuation zone information. The recommendations here recognise the requirement to balance the complexity and current uncertainty of the tsunami risk environment with the need to provide the community with easily understood emergency information.

The information in this document is consistent with:

• The tsunami content of the national Consistent Messaging Project• The National Tsunami Advisory and Warning Plan (2008)• The National Tsunami Signage Technical Standard for the CDEM Sector (TS

01/08)

Purpose of this information


A key consideration for tsunami emergency planning is the number of evacuation zones used for evacuation management, and the ways in which hazard information is communicated to the public.

Use of a single tsunami evacuation zone has the advantage of simplicity for emergency planning and public awareness and understanding. However, because a single evacuation zone must accommodate the very wide range of local risk scenarios that may exist, this can result in regular ‘over-evacuation’ of the entire zone for common small scale events. Recurring over-evacuation is likely to result in decreasing levels of community trust in emergency response arrangements.

Use of more than three or four evacuation zones may more accurately reflect the range of local tsunami risk scenarios. However, such differentiation requires far greater resources and a higher degree of coordination for planning and response, and the complexity of information may create public misunderstanding.

The use of at least two and a maximum of three evacuation zones is recommended for nationally consistent tsunami emergency planning in New Zealand communities. The recommended standard for distinguishing the three evacuation zones on evacuation maps is the use of the colours red, orange, and yellow. The characteristics of each of the three zones are given below.

█ Red zoneThe red zone is intended as a shore-exclusion zone that can be designated off limits in the event of any expected tsunami. This represents the highest risk zone and is the first place people should evacuate from in any sort of tsunami warning. People could expect ‘activation’ of this zone several times during their life.

█ Orange zoneThe orange zone is intended to be the area evacuated in most if not all distant- and regional-source official warnings (i.e., warnings that extend beyond the red zone, for tsunami from sources more than one hour of travel time away from the mapped location). Local differentiation of this zone can be achieved using terms that are familiar to the community such as street names and key landmarks.

█ Yellow zoneThe yellow zone should cover all maximum credible tsunami, including the highest impact events. The intention is that the yellow zone provides for local-source maximum credible events, based on locally determined risk. People should evacuate this zone in natural or informal warnings from a local source event.The yellow zone may be removed from published, publicly available evacuation maps in a region where the orange zone includes the local-source maximum credible tsunami. In this case it is very important that the boundaries of the orange zone are particularly cautious – that is, there should be negligible chance an official evacuation will be called that requires evacuation of an area larger than the mapped orange zone.

Tsunami evacuation zones

Introduction

The optimum number of evacuation zones

Recommended number of tsunami evacuation zones


The three evacuation zones – red, orange and yellow – are colour-coded for visual distinction in colour publications, but should also be depicted in words to ensure clarity on photocopied or greyscale reproductions.

While the risk criteria for each zone are described above in general terms, this guideline does not prescribe the methodology by which the local tsunami risk is assessed. The elevations used to establish tsunami evacuation zone boundaries are developed at local level, based on location-specific hazard analysis and risk assessment.

The next section, ‘Defining evacuation zone boundaries’, provides more detail regarding criteria for defining evacuation zones, and how existing local hazard information may be incorporated or aligned to fit the recommendations in this guideline. It also illustrates the four levels of technical development for establishing evacuation zone boundaries. The recommended minimum technical standard is development level 2.

Recommended number of tsunami evacuation zones(continued)

Establishing evacuation zone boundaries

Tsunami evacuation zones (continued)


Defining evacuation zone boundaries

Evacuation zone boundaries can be determined using a variety of hazard models. Zones ideally need to represent an envelope around all possible inundations from all known tsunami sources, taking into account all of the ways each of those sources may generate a tsunami. The high degree of uncertainty in tsunami source models, and the very time consuming and resource intensive nature of modelling make this comprehensive approach to tsunami risk assessment unlikely in the short term.

The recommended approach to developing tsunami evacuation zones is to map now, and progressively refine the accuracy of boundaries as the science improves over time.

Four developmental levels (1-4) are recognised for establishing tsunami evacuation zone boundaries.

Figure 1: Cross section showing how evacuation zone boundaries can be mapped using a projection of wave heights inland, based on a simple ‘bathtub’ model.

Evacuation zone boundaries

Scenario wave heights

Projection of wave height inland, with a topographic arbitrary cut-off

Level 1 Is a simple ‘bathtub’ model in which inundation is determined based on a maximum wave height (Fig. 1), projected inland from the coast to some cut-off elevation. This approach provides the crudest and simplest method of mapping evacuation zones.

Introduction

Four developmental levels


Figure 2: Cross-section at the coast showing how evacuation zone boundaries are determined using an attenuation rule (Development Level 2), in which elevation decreases from a maximum wave height at the coast and is projected inland according to some slope angle.

Level 3 Is a computer-derived simulation model that theoretically allows for complexities that a simpler ‘rule’ cannot, such as varied surface roughness from different land uses, and water turning corners and travelling laterally to the coast on its inundation path. Such modelling is expensive and the quality of outputs is dependent on the science behind the hazard model.

Level 4 Is the most complete modelling, based on an envelope around all inundations from multiple well-tested computer models. Development to this level of sophistication will require a comprehensive scientific understanding of all possible tsunami sources (distant, regional and local), wave propagation and inundation behaviours, across a range of magnitudes.

Level 2 Uses a measure of rule-based wave height attenuation inland from the coast (Fig. 2). GIS can be utilised for applying the attenuation rule. This approach derives a more realistic output than a simple ‘bathtub’ model but is still a rough estimation which cannot account for physical variations in wave behaviour. This rule does not account for all scenarios and improvements are expected to come with time. Local knowledge must also be applied to support the process.

Evacuation zone boundaries

Scenario wave heights

Attenuation rule = 1m decrease inland every 200m. Up-river attenuation rule = 1m decrease every 400m.

Defining evacuation zone boundaries (continued)

Four developmental levels (continued)


As the understanding of local tsunami hazard and risk improves, Local Authorities and CDEM Groups should be looking to advance the level of technical sophistication used in defining tsunami hazard and evacuation zones. Until higher stage assessments can be undertaken, a precautionary approach is recommended in defining the placement of evacuation zone boundaries. The recommended minimum development standard for defining tsunami evacuation zone boundaries is the application of a model consistent with developmental Level 2 (rule-based approximation).

An initial step for small coastal communities with limited resources for risk mapping might be to agree the entire settlement is within the orange evacuation zone until Level 2 or higher stage assessments can be undertaken.

Even though tsunami evacuation zone boundaries may change in the future, the components, colours, and style of the maps will not need to change. This is important for sustaining community awareness and inter-generational tsunami readiness.

The specific method used to define hazard zone boundaries and the level of risk being managed is up to Local Authorities to decide for themselves, in close consultation with their communities.

Many Local Authorities or CDEM Groups have gone to some considerable effort to define and map tsunami (and storm surge) risk areas, based on recognised research and modelling. The guidance provided in this document is expected to accommodate any existing tsunami hazard maps and to support the communication of evacuation information in a consistent manner nationally. The recommendations presented here aim to be, wherever possible, compatible with the content and methodology of any existing hazard zones.

In some cases, existing zones will be aiming to cover the maximum credible event tsunami, in which case these would be drawn under the guidelines as the ‘yellow zone’. In other cases existing zones will be aiming to only cover distant-source tsunami. These would be drawn under these guidelines as the ‘orange zone’. If only one or the other currently exists it is recommended that the complementary zone is included and a ‘red zone’ (the shore exclusion zone) added.

Elevations used must be wave at shore, offshore, above Mean High Water Spring. Run-up could be twice as high on steep, low-friction slopes near the coast. Thus, evacuation zones should be based on an elevation at the coast which is twice the predicted offshore wave height(s).

Factors unique to an area that may impact on planning arrangements must also be carefully identified and taken into account. Consideration should also be given to how the natural, built, social, and economic components of a community


Minimum standard and improving zone boundaries over time

Accommodating existing hazard or evacuation zone information

Other considerations in defining evacuation zones


might be expected to change over the medium to long term. Examples include the potential for sea level rise and increased storm activity through climate change, or increases in the number of older retired people living in certain coastal areas. Vertical evacuation (e.g. evacuation upstairs in/on buildings or structures) options also need to be locally considered, and where planned for should be indicated on tsunami evacuation maps and supported with signage.

Other considerations in developing evacuation zones(continued)


Maps of evacuation zones and routes are critical for communicating tsunami risk and emergency response information to the public, and for providing a common platform for integrated evacuation planning.

In addition to the number and appearance of evacuation zones on maps, the basic legend, instruction messages and supporting information on maps should be nationally consistent. To ensure common understanding across New Zealand communities, maps should use the same or closely similar colours, the same names for evacuation zones, and common symbols. A balance is required between oversimplification and excessive detail.

Maps should be produced to a scale appropriate to the area shown. Note that scale can give a false impression of accuracy if not carefully managed. For zones developed using 20 metre contour data, and maps using 1:50,000 topographic data, it may be necessary to refine the zone boundaries with detailed local information if enlarging beyond 1:25,000.

For high density urban areas it is recommended that higher resolution elevation data are used (e.g. LiDAR1), and additional information sources are included on maps to improve recognition and readability; for example, elements from council cadastral maps showing named streets, or aerial photo imagery that clearly identifies well known geographical features.

Features that are added should be appropriate for the map scale and population density. For example, in urban areas detailed street maps might be required with careful consideration given to expanding zone boundary locations as needed to accommodate street layout and the location of key facilities such as schools or hospitals.

It is recommended that, as a minimum, all of the following should be included on maps and shown in the legend:

• Red Zone• Orange Zone • Yellow Zone• Tsunami Safe Area or Locations• Key buildings/urban areas• Roads• Rivers• Evacuation routes


Maps of evacuation zones and routes are critical for communicating tsunami risk and emergency response information to the public, and for providing a common platform for integrated evacuation planning.

In addition to the number and appearance of evacuation zones on maps, the basic legend, instruction messages and supporting information on maps should be nationally consistent. To ensure common understanding across New Zealand communities, maps should use the same or closely similar colours, the same names for evacuation zones, and common symbols. A balance is required between oversimplification and excessive detail.

Maps should be produced to a scale appropriate to the area shown. Note that scale can give a false impression of accuracy if not carefully managed. For zones developed using 20 metre contour data, and maps using 1:50,000 topographic data, it may be necessary to refine the zone boundaries with detailed local information if enlarging beyond 1:25,000.

For high density urban areas it is recommended that higher resolution elevation data are used (e.g. LiDAR1), and additional information sources are included on maps to improve recognition and readability; for example, elements from council cadastral maps showing named streets, or aerial photo imagery that clearly identifies well known geographical features.

Features that are added should be appropriate for the map scale and population density. For example, in urban areas detailed street maps might be required with careful consideration given to expanding zone boundary locations as needed to accommodate street layout and the location of key facilities such as schools or hospitals.

It is recommended that, as a minimum, all of the following should be included on maps and shown in the legend:

• Red Zone• Orange Zone • Yellow Zone• Tsunami Safe Area or Locations• Key buildings/urban areas• Roads• Rivers• Evacuation routes

Introduction

Tsunami evacuation maps

Local customisation of maps is encouraged to ensure information relevant to a community is included, for e.g. the location of special areas of interest such as marae, or local knowledge such as the safety of a particular pathway or route.

Map scale

Legend text

1. LiDAR = (Light Detection and Ranging) is an optical remote sensing technology that measures properties of scattered light (principally laser pulses) to find range and/or other information of a distant target.


In ‘natural’ or ‘informal’ warnings people are expected to evacuate all zones.

In ‘official’ warnings from Civil Defence Emergency Management, people are expected to evacuate the zone(s) stated in the warning message.

Evacuation should be on foot (or bicycle) wherever possible.

Community engagement and public education are essential for improving the understanding of what to look for and what to do during a tsunami. Ideally, communities should plan their own evacuation routes (with assistance from local CDEM), and exercise plans on a regular basis.

The following text is recommended for inclusion on maps under the following headings. This text has been developed by the cross-agency Consistent Messaging Project.

Natural Warnings In the case of a large earthquake (one it is hard to stand up in), unusual noises from the ocean, or changes in the ocean (e.g. the ocean rushing in or out), or you feel a weak earthquake that lasts for a minute or more:Evacuate ALL zones. A wave may arrive within minutes or take more than an hour to arrive. Wait for official all clear or advice from Civil Defence Emergency Management

Official WarningsReceived from local Civil Defence Emergency Management. These warnings may come to you via New Zealand TV/radio broadcasts or the emergency services. You may receive warnings from one or several sources.Evacuate from the zone(s) stated in the warning message. Wait for official all clear or advice from Civil Defence Emergency Management

Informal WarningsWarnings from friends, other members of the public, international media, etc may be correct. If you feel the threat is imminent, quickly get to high ground. Consider evacuating from all zones. Verify the warning only once evacuated or if you can do so quickly via radio, television, internet, or through your nearest civil defence emergency management office.

Tsunami evacuation maps (continued)

Principles for warning and evacuation information on maps

Recommended text for warning and evacuation information


Local customisationInformation on specific local response arrangements should be explained, for example, that public alerts may be through siren, telephone, loud hailer or other arrangements.

Tsunami Evacuation• Evacuate via the routes drawn on this map• Follow signed routes where present.• Walk quickly if possible, drive only if essential. If driving, keep going once you

are well outside all evacuation zones to allow room for others behind you.• The first waves may not be the largest.• There may be multiple waves separated by up to an hour, or more. Large waves

may come after a series of smaller waves. The largest waves from distant sources may take many hours to arrive.

• Stay OUT of evacuation zones until given the official all clear from Civil Defence Emergency Management.

• Stay away from the Red Zone for at least 24 hours after any tsunami warning – even small waves can create dangerous currents.


Recommended text for warning and evacuation information (continued)

Maps depicting tsunami evacuation zones, escape routes and tsunami safe areas need to be available as required by the community. It is recommended that maps are available for display in homes, holiday homes, tourist facilities, workplaces and public buildings in areas subject to tsunami risk.

High-use coastal areas should prominently display evacuation maps as part of tsunami information boards. Maps should be prepared and delivered in conjunction with planned tsunami signage placement, which depict evacuation zones and routes on the ground.

Placement and availability


YELLOW ZONE

ORANGE ZONE

An example is provided here showing the appearance of an information board using the guidelines contained in this section.

Information board example



Signage is an integral part of practical tsunami risk management. Signage depicting evacuation zones and routes raises public awareness of local tsunami risk and provides information to increase the efficiency and effectiveness of an evacuation. Well placed evacuation signage is the critical link between the emergency response plan and an actual event.

The following is a summary of the guidance on types and placement of tsunami signage contained within the National Tsunami Signage Technical Standard (MCDEM 2008a).

1. ‘Evacuation Zone’ signs are designed to be placed within the evacuation zones, especially at the coast – to clearly indicate that this place is within the evacuation zone.

2. ‘Information Boards’ are intended to house evacuation maps and supporting information.

3. ‘Evacuation Route’ signs are designed to delineate the route from within the zone to beyond the boundary of the evacuation zone. These signs would be placed after the evacuation routes have been drawn and exercised on evacuation zone maps. For routes where driving may be used for evacuation these signs must continue for some distance into the safe area to avoid people stopping early and blocking cars behind within the evacuation zone.

4. ‘Safe Location’ signs must be within safe areas and are recommended primarily for walking or cycling evacuation routes because of the potential for drivers to stop at them and block those behind them. If used for routes where driving is possible these signs must be a substantial distance within safe areas.

5. ‘Previous event’ signs, if used, should be for maximum events only and would be expected by their nature to lie within but near the boundary of the yellow zone.

Signage for tsunami information

Introduction

National Tsunami Signage Technical Standard summary


Part of the vision for a ‘Resilient New Zealand’ is that individuals and communities understand and manage their own hazard risks. Arrangements to support this are best developed at the local level. Community groups possess the knowledge of, relationships with, and the resources for assisting their own community.

As a general rule, communities should be engaged early and often, with opportunities provided for the community to lead plan development. This will be easiest where strong, networked community group structures are well established.

Careful consideration needs to be given to the range of unique stakeholders that may exist, for instance, transient beach users, holiday home owners, permanent residents, businesses, recreational boaters etc.

The development of tsunami evacuation plans and maps might be undertaken as a specific emergency planning initiative, or could be approached as one component of a wider programme of community development work.

Further planning guidance is available in the Mass Evacuation Planning Director’s Guideline (DGL07/08).

Community participation in evacuation planning


Berryman, K. (compiler), 2005. Review of Tsunami Hazard and Risk in New Zealand. GNS Science client report CR2005-104, Lower Hutt.

Leonard, G. (compiler), 2008. Draft guidelines for consistent New Zealand tsunami evacuation mapping. GNS Science Report SR2008/30, Lower Hutt. 18p.

Ministry of Civil Defence & Emergency Management (MCDEM), 2008a. National Tsunami Signage, Technical Standard for the CDEM Sector [TS01/08]. Wellington. 19p.

Ministry of Civil Defence & Emergency Management (MCDEM), 2008b. National Tsunami Advisory and Warning Plan. Wellington. 15p.

Webb T. (compiler), 2005. Review of New Zealand’s preparedness for tsunami hazard, comparison to risk and recommendations for treatment. GNS Science Client Report 2005/162, 104 p. plus appendices.

References


www.civildefence.govt.nz

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